Temperature sign
From above

Seismograph and Bluebell Pools are located at the West Thumb Geyser Basin in Yellowstone. The two pools are blue in color. The Seismograph pool occasionally collects mud from nearby mudpots.

Both can be viewed from the outer loop of the Trail. A steep grade connects the outer loop boardwalk with the inner loop. The two pools are located next to that grade. The bright blue color is due to extremely high temperatures, usually around 165 degrees F.


Nearby hydrothermal features include the Black Pool, Fishing Cone and the Abyss Pool.